The invention relates to a refrigeration system for a refrigerant heating type air conditioning apparatus, and more particularly to an air conditioning apparatus for withdrawing refrigerant from a heat exchanger located outdoors.
A heat pump type air conditioning apparatus generally has a drawback in that its heating capacity is reduced with a fall in atmospheric temperature. Therefore an air conditioning apparatus has been developed which is provided with a refrigerant heating device designed to heat the refrigerant by, for example, a gas burner or electric heater during the cold season to make up for the decline in the heating capacity of the apparatus.
A conventional refrigerant system of a refrigerant heating type air conditioning apparatus, sometimes referred to as a heat pump, is shown in FIG. 1. the refrigerant system has a main circuit 1, including a compressor 2, a four-way valve 3, having ports a, b, c and d, a heat exchanger 4 located outdoors, a main capillary tube 5, check valves 6, 7, a heat exchanger 8 located indoors, an evaporator 18, and an accumulator 9.
The refrigerant system further has a refrigerant heating device 10 for heating the evaporator 18 and an electromagnetic valve 11 so that refrigerant may bypass the exchanger 4 during the heating operation. The compressor 2 is also connected with a releasing circuit 12 which acts to return a portion of the refrigerant from the pressure chamber of the compressor 2 towards the suction side thereof for balanced heating and cooling capacity of the system. The releasing circuit 12 includes an electromagnetic valve 13 and a capillary tube 14. Further, a refrigerant withdrawing circuit 15 is provided for the outdoor heat exchanger 4 so as to withdraw the remaining refrigerant therefrom during the heating operation. The withdrawing circuit 15 has check valves 16, 17, as shown in FIG. 1.
During the heating operation, the four-way valve 3 is opened connecting ports a and b together and c and d together, so as to connect compressor 2 with indoor heat exchanger 8. Further, both electromagnetic valves 11 and 13 are also opened so as to heat refrigerant in the refrigerant heating device 10. During the heating cycle, the refrigerant flows in the refrigerant system, as shown by solid arrows in FIG. 1.
In the cooling cycle, four-way valve 3 is opened to connect ports a and c together and ports b and d together, and valves 11 and 13 are closed. Refrigerant flows in the direction of the dotted arrows through heat exchanger 4, main capillary tube 5, check valve 6, heat exchanger 8, four-way valve 3, check valve 7 and accumulator 9.
In the heating operation, the refrigerant heating type air conditioning apparatus generally has a drawback in that the heating capacity is reduced with a fall in atmospheric temperature in part because of accumulated refrigerant within the outdoor heat exchanger 4. Such refrigerant condenses and accumulates in the outdoor heat exchanger 4 and results from leakage from check valves 6 and 7 and also leakage from compressor 2 through four-way valve 3 during operation of valve 3.
Therefore, conventional apparatus acts so as to withdraw the refrigerant from exchanger 4 with the start of each heating operation, or when a predetermined amount of refrigerant is accumulated therein, as described hereinafter.
In the refrigerant withdrawing operation, the compressor 2 pumps the refrigerant after closing electromagnetic valves 11, 13 and opening four-way valve 3, thereby connecting ports a and b together as well as ports c and d together. In this case, the refrigerant in the outdoor heat exchanger 4 is withdrawn via the suction pressure of the compressor 2 into the inlet side of compressor 2 through the withdrawing circuit 15, check valve 17, four-way valve 3, and check valve 7. However, since the refrigerant withdrawing circuit 15 is isolated from the refrigerant high pressure via valves 6 and 11, the suction side of compressor 2 has no connection with the high pressure side. Therefore, the compressor 2 does not operate in its normal mode of operation and often is unreliable when operated once again in its normal mode. Additionally, there is a drawback that the heating operation is stopped during the refrigerant withdrawing operation.